Generally, a solenoid valve is mainly classified into a hydraulic pressure solenoid valve used in a hydraulic circuit, an air solenoid valve used in a pneumatic circuit, a solenoid valve merely using an electromagnetic force, or the like.
Among those, the hydraulic pressure solenoid valve controls a flow of a hydraulic pressure generated from a hydraulic pressure pump to start, stop, change a motion direction of an operating device, or the like.
For example, the hydraulic pressure solenoid valve may be used in the operating devices such as an automatic transmission of a vehicle. The automatic transmission includes a plurality of friction elements such as a clutch and a brake operated by the hydraulic pressure to implement various shift stages. That is, the hydraulic pressure solenoid valve controls an operation of the friction elements. In particular, when the hydraulic pressure solenoid valve is installed at an engine clutch of a hybrid vehicle, an operation of the hydraulic pressure solenoid valve determines basic performance of the hybrid vehicle selectively connecting between an engine and a motor.
However, when foreign materials introduced into the solenoid valve affect an internal pressure of the solenoid valve, automatic transmission performance of the engine-driven vehicle or the hybrid vehicle may deteriorate. The deterioration in performance of the automatic transmission has an adverse effect on driver satisfaction and may cause a severe accident.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.